This disclosure relates to an energy supply device for providing energy for an electrically operable vehicle. The disclosure further relates to a method for charging an energy supply device of this kind.
Many electrically operable vehicles require an electrical AC voltage, which is often a single- or three-phase voltage, in order to be supplied with power. The prior art discloses electrical energy storage devices which comprise a large number of energy cell modules which each comprise an electrochemical cell. Several of the energy cell modules are interconnected in series and form an energy supply branch. The electrochemical cells of the individual energy cell modules can be coupled into their energy supply branch by means of a coupling device, for example a 4-quadrant actuator. The voltage which is generated by an electrochemical cell can be coupled into the energy supply branch with a different polarity, so that both positive and also negative voltages can be generated by way of one energy supply branch. As an alternative, the electrochemical cell can be decoupled and bridged by generating a short circuit between the integration connections of the energy cell module in the series circuit, this being called the bypass mode. For the purpose of charging an energy cell module, the electrochemical cell of said energy cell module is coupled into the energy supply branch in such a way that the voltage of said energy cell module is directed against a charging voltage. For discharging purposes, or for supplying power to a load, the electrochemical cell is coupled into the energy supply branch with a polarity with which current flows through the load in the correct direction. Owing to the energy cell modules being coupled-in in a coordinated manner, an AC voltage with a frequency which can be freely selected within operating limits can be generated. An energy storage device of this kind is called a Battery Direct Inverter (BDI). A BDI behaves, at its energy supply connections, like a conventional converter with an intermediate circuit. Therefore, all loads which can be connected to a conventional converter can also be connected to a BDI. An example of a BDI of this kind from the prior art is disclosed in WO 2012/159811.
So-called range extenders are known for use in electrically driven vehicles. Said range extenders comprise a generator which can be driven by way of an internal combustion engine. The internal combustion engine is started when the energy content of the energy storage device falls below a critical threshold, and then drives the generator. The battery is charged by way of the generator via rectifiers. A drive motor is supplied with electrical energy from the battery via an inverter. In one variant, the drive motor can also be supplied with power from the generator. The battery is usually arranged in a DC voltage intermediate circuit.